Storytelling plays an important role in providing an engaging player experience in modem
computer games. Typically in single-player games, stories are highly linear and carefully
scripted by the story authors, with events occurring in exact pre-specified sequences. This
method of storytelling can result in a highly crafted experience that helps to enhance player
immersion in the game world. Storytelling in multiplayer online game worlds, as in their
single-player counterparts, also tends to be based on a set of highly scripted stories.
However, the technical problems caused by the presence of many players in these worlds are
typically dealt with by various devices or tricks that are inherently detrimental to the
storytelling experience. The devices used include observable world state manipulation by
the system and allowing player actions to have only limited consequences in the world. Both
techniques diminish the believability of the storyworld and are likely to reduce player
enjoyment of the game narrative. An improved method of storytelling in multiplayer games
is therefore needed to address this problem. It is demonstrated in this thesis that a more
adaptive and effective approach to storytelling in multiplayer game worlds can be provided
by incorporating hierarchical task network (HTN) planning as part of a wider story
management process. A novel approach to story authoring and management in dynamic,
multiplayer worlds is presented in which the methods from which story plans are generated
are defined by the story author in the HTN formalism. The story authoring and management
techniques presented in the thesis include a story repair method that detects and responds to
events that threaten to invalidate an ongoing story plan, and an extension of the HTN
formalism to enable player interaction at a higher level of abstraction than that used for the
enactment of generated stories. A virtual world designed to provide the richness and
variability required for adaptive storytelling in a multiplayer environment is also presented
as a basis for evaluation of the proposed methodology. The results presented in the thesis
demonstrate the effectiveness of the proposed approach to story authoring and management
in terms of the adaptability, variability, and robustness of the stories created in a
dynamically changing, multiplayer environment.